Re: [PATCH v3 23/55] KVM: arm/arm64: vgic-new: Add CTLR, TYPER and IIDR handlers

[Andre Przywara <andre.przywara@arm.com>]

Hej,

On 11/05/16 13:05, Christoffer Dall wrote:
> On Fri, May 06, 2016 at 11:45:36AM +0100, Andre Przywara wrote:
>> From: Marc Zyngier <marc.zyngier@arm.com>
>>
>> Those three registers are v2 emulation specific, so their implementation
>> lives entirely in vgic-mmio-v2.c. Also they are handled in one function,
>> as their implementation is pretty simple.
>> When the guest enables the distributor, we kick all VCPUs to get
>> potentially pending interrupts serviced.
>>
>> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
>> Signed-off-by: Andre Przywara <andre.przywara@arm.com>
>> ---
>> Changelog RFC..v1:
>> - kick VCPUs is the distributor gets enabled
>> - improve comment
>>
>> Changelog v1 .. v2:
>> - adapt to new MMIO framework
>> - use switch() statements to improve readability
>>
>> Changelog v2 .. v3:
>> - add vgic_kick_vcpus() implementation
>>
>>  include/linux/irqchip/arm-gic.h  |  1 +
>>  virt/kvm/arm/vgic/vgic-mmio-v2.c | 48 +++++++++++++++++++++++++++++++++++++++-
>>  virt/kvm/arm/vgic/vgic.c         | 15 +++++++++++++
>>  virt/kvm/arm/vgic/vgic.h         |  4 ++++
>>  4 files changed, 67 insertions(+), 1 deletion(-)
>>
>> diff --git a/include/linux/irqchip/arm-gic.h b/include/linux/irqchip/arm-gic.h
>> index be0d26f..fd05185 100644
>> --- a/include/linux/irqchip/arm-gic.h
>> +++ b/include/linux/irqchip/arm-gic.h
>> @@ -33,6 +33,7 @@
>>  
>>  #define GIC_DIST_CTRL			0x000
>>  #define GIC_DIST_CTR			0x004
>> +#define GIC_DIST_IIDR			0x008
>>  #define GIC_DIST_IGROUP			0x080
>>  #define GIC_DIST_ENABLE_SET		0x100
>>  #define GIC_DIST_ENABLE_CLEAR		0x180
>> diff --git a/virt/kvm/arm/vgic/vgic-mmio-v2.c b/virt/kvm/arm/vgic/vgic-mmio-v2.c
>> index 2729a22..69e96f7 100644
>> --- a/virt/kvm/arm/vgic/vgic-mmio-v2.c
>> +++ b/virt/kvm/arm/vgic/vgic-mmio-v2.c
>> @@ -20,9 +20,55 @@
>>  #include "vgic.h"
>>  #include "vgic-mmio.h"
>>  
>> +static unsigned long vgic_mmio_read_v2_misc(struct kvm_vcpu *vcpu,
>> +					    gpa_t addr, unsigned int len)
>> +{
>> +	u32 value;
>> +
>> +	switch (addr & 0x0c) {
>> +	case GIC_DIST_CTRL:
>> +		value = vcpu->kvm->arch.vgic.enabled ? GICD_ENABLE : 0;
>> +		break;
>> +	case GIC_DIST_CTR:
>> +		value = vcpu->kvm->arch.vgic.nr_spis + VGIC_NR_PRIVATE_IRQS;
>> +		value = (value >> 5) - 1;
>> +		value |= (atomic_read(&vcpu->kvm->online_vcpus) - 1) << 5;
>> +		break;
>> +	case GIC_DIST_IIDR:
>> +		value = (PRODUCT_ID_KVM << 24) | (IMPLEMENTER_ARM << 0);
>> +		break;
>> +	default:
>> +		return 0;
>> +	}
>> +
>> +	return extract_bytes(value, addr & 3, len);
>> +}
>> +
>> +static void vgic_mmio_write_v2_misc(struct kvm_vcpu *vcpu,
>> +				    gpa_t addr, unsigned int len,
>> +				    unsigned long val)
>> +{
>> +	switch (addr & 0x0c) {
>> +	case GIC_DIST_CTRL:
>> +		if (!(addr & 1)) {
> 
> what is this !(addr & 1) check?

Mmmh, interesting. The original idea was that we care only about the
lowest significant byte. I guess this was somehow lost in translation
when Marc reworked the function. I think it should at least read:
"if (!(addr & 3))" to match the switch mask, otherwise for instance a
byte write to address 2 triggers the if branch as well.

I will fix the mask to 3 and add a comment.

Thanks,
Andre.


> 
>> +			struct vgic_dist *dist = &vcpu->kvm->arch.vgic;
>> +			bool was_enabled = dist->enabled;
>> +
>> +			dist->enabled = val & GICD_ENABLE;
>> +			if (!was_enabled && dist->enabled)
>> +				vgic_kick_vcpus(vcpu->kvm);
>> +		}
>> +		break;
>> +	case GIC_DIST_CTR:
>> +	case GIC_DIST_IIDR:
>> +		/* Nothing to do */
>> +		return;
>> +	}
>> +}
>> +
>>  static const struct vgic_register_region vgic_v2_dist_registers[] = {
>>  	REGISTER_DESC_WITH_LENGTH(GIC_DIST_CTRL,
>> -		vgic_mmio_read_raz, vgic_mmio_write_wi, 12),
>> +		vgic_mmio_read_v2_misc, vgic_mmio_write_v2_misc, 12),
>>  	REGISTER_DESC_WITH_BITS_PER_IRQ(GIC_DIST_IGROUP,
>>  		vgic_mmio_read_rao, vgic_mmio_write_wi, 1),
>>  	REGISTER_DESC_WITH_BITS_PER_IRQ(GIC_DIST_ENABLE_SET,
>> diff --git a/virt/kvm/arm/vgic/vgic.c b/virt/kvm/arm/vgic/vgic.c
>> index c3dbcf3..5355de6 100644
>> --- a/virt/kvm/arm/vgic/vgic.c
>> +++ b/virt/kvm/arm/vgic/vgic.c
>> @@ -544,3 +544,18 @@ int kvm_vgic_vcpu_pending_irq(struct kvm_vcpu *vcpu)
>>  
>>  	return pending;
>>  }
>> +
>> +void vgic_kick_vcpus(struct kvm *kvm)
>> +{
>> +	struct kvm_vcpu *vcpu;
>> +	int c;
>> +
>> +	/*
>> +	 * We've injected an interrupt, time to find out who deserves
>> +	 * a good kick...
>> +	 */
>> +	kvm_for_each_vcpu(c, vcpu, kvm) {
>> +		if (kvm_vgic_vcpu_pending_irq(vcpu))
>> +			kvm_vcpu_kick(vcpu);
>> +	}
>> +}
>> diff --git a/virt/kvm/arm/vgic/vgic.h b/virt/kvm/arm/vgic/vgic.h
>> index fd9acaa..cf62015 100644
>> --- a/virt/kvm/arm/vgic/vgic.h
>> +++ b/virt/kvm/arm/vgic/vgic.h
>> @@ -16,11 +16,15 @@
>>  #ifndef __KVM_ARM_VGIC_NEW_H__
>>  #define __KVM_ARM_VGIC_NEW_H__
>>  
>> +#define PRODUCT_ID_KVM		0x4b	/* ASCII code K */
>> +#define IMPLEMENTER_ARM		0x43b
>> +
>>  #define vgic_irq_is_sgi(intid) ((intid) < VGIC_NR_SGIS)
>>  
>>  struct vgic_irq *vgic_get_irq(struct kvm *kvm, struct kvm_vcpu *vcpu,
>>  			      u32 intid);
>>  bool vgic_queue_irq_unlock(struct kvm *kvm, struct vgic_irq *irq);
>> +void vgic_kick_vcpus(struct kvm *kvm);
>>  
>>  void vgic_v2_process_maintenance(struct kvm_vcpu *vcpu);
>>  void vgic_v2_fold_lr_state(struct kvm_vcpu *vcpu);
>> -- 
>> 2.7.3
>>
>> --
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